The invention relates to interactive computer graphics systems.
Curves are often depicted as graphics in computer graphics systems. However, curves are typically difficult to draw with freehand gestures using input devices such as a mouse or graphics tablet. Undesirable bumps and flat portions often result.
When an artist is drawing with pen and paper, the artist can modify a curve by drawing another line or curve in an area that is undesirable, covering the undesirable portion. The repeated addition of lines and curves is sometimes referred to as "sketching". In a computer graphics system where curves are represented by mathematical formulas, it may be undesirable to layer one curve over another to achieve the appearance of a single desired curve.
Conventional graphics systems offer some curve editing functionality. One approach is to redraw the curve. Another is to manipulate "control handles" which define the curve. Both of these approaches are often time consuming and inconvenient.
Similar problems exist in editing brush stokes in computer graphics systems. Again, adding layers of curves or brush strokes over an undesirable portion is slow and prone to the same errors which caused the undesirable portion in the first place.